Kang Xi, Abroshan Hadi, Wang Shuxin, Zhu Manzhou
Department of Chemistry and Center for Atomic Engineering of Advanced Materials, Anhui Province Key Laboratory of Chemistry for Inorganic/Organic Hybrid Functionalized Materials , Anhui University , Hefei 230601 , Anhui , China.
SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering , Stanford University , 443 Via Ortega , Stanford 94305 , California , United States.
Inorg Chem. 2019 Aug 19;58(16):11000-11009. doi: 10.1021/acs.inorgchem.9b01545. Epub 2019 Aug 6.
Metal nanoclusters have attracted extensive interests owing to their atomically precise structures as well as intriguing properties. However, silver nanoclusters are not as stable as their gold counterparts, impeding the practical applications of Ag nanoclusters. In this work, a strategy of free valence electron centralization was exploited to render parent Ag nanoclusters highly stable. The stability of Ag(SSR)(PPh) (SSR: benzene-1,3-dithiol) was controllably enhanced by stepwisely alloying the Ag nanocluster to AgCu(SSR)(PPh) and AuAgCu(SSR)(PPh). Specifically, the trimetallic AuAgCu is ultrastable even at 175 °C, which is close to the nanocluster decomposition temperature. The structures of AgCu and AuAgCu nanoclusters are determined by single-crystal X-ray diffraction. Furthermore, a combination of X-ray photoelectron spectroscopy measurements and density functional theory calculations demonstrates that the enhanced stability is induced by the centralization of the free valence electrons to the interior of the nanocluster. More importantly, the AuAgCu enables the multicomponent A coupling reaction at high temperatures, which remarkably shortens the catalytic reaction time from ∼5 h to 3 min. Overall, this work presents a strategy for enhancing the thermal stability of nanoclusters via centralizing the free valence electrons to the nanocluster kernels.
金属纳米团簇因其原子精确的结构以及有趣的性质而引起了广泛关注。然而，银纳米团簇不如其金纳米团簇稳定，这阻碍了银纳米团簇的实际应用。在这项工作中，我们采用了一种自由价电子集中化策略，以使母体银纳米团簇具有高度稳定性。通过将银纳米团簇逐步合金化为AgCu(SSR)(PPh)和AuAgCu(SSR)(PPh)，可控地提高了Ag(SSR)(PPh)（SSR：苯-1,3-二硫醇）的稳定性。具体而言，即使在175°C（接近纳米团簇分解温度）下，三金属AuAgCu也是超稳定的。通过单晶X射线衍射确定了AgCu和AuAgCu纳米团簇的结构。此外，结合X射线光电子能谱测量和密度泛函理论计算表明，自由价电子向纳米团簇内部的集中导致了稳定性的增强。更重要的是，AuAgCu能够在高温下实现多组分A偶联反应，这显著缩短了催化反应时间，从约5小时缩短至3分钟。总的来说，这项工作提出了一种通过将自由价电子集中到纳米团簇核心来提高纳米团簇热稳定性的策略。
